Sunday, November 3, 2019

Plant Common Names--Rules and Customs

Solanum lycopersicum, tomato
tomato, Solanum lycopersicum
The scientific community has given every plant a single scientific name, written as if it were in Latin (link). But mostly people call plants by a common name, one in the local language. Many--if not most--common names are unlike the scientific name.
apple tree, Malus domestica
apple tree, Malus domestica
Scientific names are agreed upon by the scientific community and there is only one per plant.

Common names have no rules. I can call it Osage orange and you can say bodark, and we're both right.

We can call two plants by the same common name--marigold for both the plants below.

marigold, genus Calendula
marigold, genus Tagetes

Of course, synonyms and duplicate names create confusion. That's why scientific names were created.

There are no rules for writing common names either. Modern American English doesn't capitalize much of anything and that includes plant common names. If the common name includes a proper noun, such as Canada thistle and Queen Anne's lace, then, yes, a capital is called for, but only for the person or place, not the whole plant name. That is a very, very strong custom in North America. But not a rule.  English classes teach us rules of grammar and what to do with plant names generally is not specified.
Canada thistle
Canada thistle, Cirsium arvense
Recently, I discovered publications from the director of the Royal Botanic Gardens in Melbourne, Australia, Tim Entwisle, that capitalized the plant common names (link). What??? So I had an email conversation with him and discovered that, his capitalization was based on a convention suggested by Spencer, Cross and Lumley in their book on plant nomenclature. Capitals were not haphazard, but according to a set of rules, so for example you wouldn't capitalize general terms like violet and oak, but you would capitalize particular species, such as Prairie Violet and Bur Oak.

I looked at other sites in the English-speaking world: in Canada, in England, in India, across Australia. This custom seems to be confined to the Royal Botanic Garden in Melbourne, Victoria, Australia.

But, truly, there is no rule on common names. Custom only. Animal names are not generally capitalized. Birds are the exception. Bird-watchers have chosen a single, official, common name for each bird, and they capitalize those. Even that is not recognized by other fields; in my general ecology text books, for example, bird names (red crossbill, cattle egret) were not capitalized.

There are rules for English. Modern English does not capitalize nouns except for proper nouns, which are persons, places, or things. Another website defined proper nouns as being one-of-a-kind. So I'd say current usage implies that a whole plant or animal species is too many different individuals to be capitalized. You would of course capitalize an animal or plant individual name: the dog Lassie or General Sherman, one of the giant sequoias, or my Christmas cactus, Junior. But that is as close as the rules get, as far as I can tell.

plant named Junior
A Christmas cactus named Junior
Despite having considered Spencer, Cross and Lumley's views, I won't, after 50 years, start capitalizing common names. I don't think it helps enough; when you do that some things are clearer but others are more confusing. Furthermore, virtually every scientific publisher across the world would change those capitals to lower case.

My advice: don't capitalize common names.

But, I agree with Tim Entwisle of RBG Melbourne on this: whatever you do, be consistent.

More on common names from this blog link
Spencer, R., R. Cross and R. Lumley. 2007. Plant Names: A Guide to Botanical Nomenclature. 3rd edition. CSIRO Publishing, Melbourne, Australia. link to their naming rules
Why the Christmas cactus is called Junior link

Kathy Keeler, A Wandering Botanist


  1. Thanks for clarifying a somewhat confusing issue!

  2. I checked over 20 of my field guides (both plant and animal) and the common names always had initial caps for each word. The exception was with hyphenated names (e.g., Grass-Leaved Golden-Aster or Grass-leaved Golden-aster or other variants). Some publishers will write the common name in all caps in the species description (e.g., WHITE OAK), but in the index only the initial letter is capitalized (White Oak).
    I also had a discussion on this point with the author of a wildflower field guide and she insisted that the names of flower species were proper nouns. Her publisher agreed. I guess it depends on how you interpret the "person, place or thing" criterion.
    Does the lay public care? Or even notice the difference between "white oak" and "White Oak?"

    1. I didn't address the English rules that sentences start with a capital and the words in a title are capitalized. These cause many capitals on common names. But look within the article. Is the name still capitalized there? I checked 10 relatively recent field guides in my library and 9 of 10 capitalized common names only where they begin a sentence or appear in a title, not within a sentence. Indexes are tricky: some treat every heading as the start of a sentence, needing a cap, capitalizing Bark and Seeds.

    2. You sent me back for a slower search! I didn't review all the field guides but here is a selection:

      Initial caps on all words, e.g., Upland Cotton, Atlantic Blue-Eyed Grass:

      Butterflies of Indiana; Indiana Univ. Press
      Butterflies of Georgia; Adventure Publ.
      Field Guide to the Wildflowers of Georgia and Surrounding States; University of Georgia Press
      Wildflowers of the Southern Mountains; University of Tennessee Press
      Wildflowers of Tennessee the Ohio Valley and the Southern Appalachians. Lone Pine Publishing
      A Swift Guide to Butterflies; Princeton University Press
      Audubon Society Field Guide to North American Wildflower Eastern & Western editions; Knopf, 1979

      Lower case, except when starting a sentence; e.g., Atlantic blue-eyed grass

      Native Trees of the Southeast: An Identification Guide; Timber Press
      Field Guide to Grasshoppers, Katydids and Crickets of the United States; Comstock Publ. Cornell U. Press
      Amphibians and Reptiles of Georgia; University of Georgia Press
      Forest Plants of the Southeast and their Wildlife Uses; University of Georgia Press

      There doesn't seem to be a rhyme or reason for the styles. The same publisher produces books with either style.
      Thanks for sending me down the rabbit hole on this. :-)